94 still isn't bad for computers in cars, that is still the EEC-4 and it's a very primitive computer compared to what they use now.
In 94 the speedometer might be less dependant on a computer than you might think. It's usually a little gear that goes on the end of a speed sensor. It's mostly mechanical.
I just went through this with a 91 ford pickup and it was the gear was warped from heat.
Could be a 15 dollar fix for you like it was for me.